In-situ rheological and structural characterization of milk foams in a commercial foaming device

Abstract

Processing, stability and sensorial perception of food foams are tightly related to their microstructure and flow behavior. Characterization of corresponding physical parameters is central for product development and quality control. An experimental setup enabling in-situ characterization of yield stress, gas volume fraction and bubble size distribution at different heights within a foam column created in a commercial whipping device is presented. Reliable determination of these quantities is shown. Foams made from regular and reconstituted milk have been investigated. Gas volume fraction and bubble size increase monotonically during free drainage. Related to the changes in these parameters, the yield stress increases strongly during initial drainage and weaker in mature foams. Gradients of the structural and rheological parameters along the direction of gravity increase over time. Yield stresses in these milk foams are as predicted from phenomenological modelling including the above parameters, emphasizing the reliability of the measurement setup. • In-situ characterization of milk foam shows vertical gradients in foam structure and yield stress. • Average bubble size and distribution span both increase linearly with drainage time. • Average bubble size increases with height and the gradient increases with time. • Foam yield stress and gas volume fraction increase with foam age and height in foam.